원전 해체 시 발생하는 대형 금속폐기물 자체처분 방안 연구

Abstract

Currently, 25 nuclear power plants are operating in Korea. Among them, Kori Unit 1 was permanently suspended in 2017, and full-scale decommissioning will begin in 2022. And 11 nuclear power plants will be permanently stopped by 2030 if the lifetime extension of each nuclear power plant is not extended. The IAEA expects a total of 6,200 tons of radioactive waste to be generated when dismantling one(1) PWR nuclear power plant of 900 ~ 1300 MWe. The amount of metal radioactive waste is 4,150 tons, accounting for 70% of the total waste. Therefore, if the metal radioactive wastes are properly decontaminated for self-disposal and recycling, the economic feasibility of dismantling nuclear power plants can be improved. In this study, the RESRAD-RECYCLE 3.10 computer code was used to evaluate individual and collective doses due to the recycling of radioactive metal waste from decommissioning stages. The radionuclide concentrations of the metal wastes used for the dose assessment were cited from the Kori 1 replacement steam generator dose rate analysis report conducted by the Korea Electric Power Research Institute in 1998. The total radioactivity of the steam generator is 3.3 TBq, which is 5% in the water chamber and 95% in the heat pipe. The decontamination coefficient was 1,000 and the specific radioactivity of the heat pipe after decontamination was 0.18753Bq/g and was excluded from the evaluation. Accordingly, it is assumed that half of the total weight of Kori Unit 1 steam generator is recycled. Individual and collective dose assessments were performed with increasing decontamination factors from 100 to 1000 to 100 units for recycling steam generator metal waste in this study. At the decontamination factor of 100, the individual and the collective doses in shielding block scenario were 15.300 μSv/yr and 1.53 × 10-4 man∙Sv/yr, respectively. The individual dose in the automobile scenario at the decontamination factor of 100 is exceeded the legally allowed dose. In the bridge scenario, the individual dose is 0.023 μSv/yr and collective dose is 4.99 man∙Sv/yr, and the result shows that the collective dose in this scenario is exceeded the legally acceptable dose. However, when the decontamination factor was above 500, it was found that individual and collective doses satisfy legal limits in all scenarios. In conclusion, the recycling of metal wastes generated in nuclear facilities is negative in terms of inhabitability, so it is appropriate to use recyclable metal wastes as materials for shields, devices and disposal drums of radioactive wastes in nuclear facilities.